The population of aged people living alone is expected to continue its recent upward trend. As people live longer and the social and economic circumstances continue to change, more aged people live alone having no supervision or limited attendance by caregivers, and aged spouses may be unable to properly care for each other. Such individuals suffer a high risk of accidents, and this is a major concern and even a fear for those aged people living alone.
Close monitoring is the key to avoiding or responding to such accidents or medical emergencies. While technologies are known for remotely monitoring certain physiological parameters, these tend to be cumbersome and a patient may easily forget to don the monitor if it is removed, for example, while taking a shower. Less cumbersome monitors require strategies for prolonging the life-time of the battery or other energy source which provides power for transmitting the monitored physiological parameters and which is necessarily limited by the space available for housing it. The limited power source must be used efficiently so that even a tiny battery may last for a reasonable period of time, on the order of a few months. Among many components involved in a remote monitoring device, a radio transmitter may consume over 40% of the total power, hence power saving in the radio transmitter will make a significant contribution to the extension of battery life. A power-saving wireless transmission protocol is thereby desirable for this and other power-sensitive applications.
The most power-consuming part of digital RF transmitters is often an oscillator circuit involving a CMOS power transistor, which consumes a significant amount of power only when the output is high, i.e. 1-bit. Therefore significant energy may be saved by minimizing the total duration of time the output is high.